Autogrow is a feature in SQL Server that automatically increases the size of database files when they run out of space. This feature is helpful for preventing immediate disruptions due to space constraints, ensuring the database remains operational even when it unexpectedly reaches its storage capacity.

When a database file reaches its maximum allocated size, the autogrow feature increases the file size by a predefined amount. This can be configured in terms of a fixed number of megabytes or a percentage of the current file size.  I like to go with fixed amounts as opposed a percentage.  1024MB is always 1024MB. 10% of 1024MB is different from 10% of 102400 in terms of the disk I need for the file to grow. The settings for autogrow can be adjusted for both data files (.mdf and .ndf) and log files (.ldf) individually.

In SQL Server Management Studio (SSMS), you can configure autogrow settings during the database creation process or modify them later by right-clicking the database, selecting “Properties,” and navigating to the “Files” page. Here, you can specify:

• The increment size (in MB or percentage) for autogrowth. As mentioned I like to set mine to be fixed amounts
• The maximum file size, which can be set to unlimited or a specific limit.

While autogrow is a convenient feature, relying on it as a primary means of managing database growth is not recommended. Here’s why auto grow should be used as a fallback mechanism rather than a primary strategy:

1. Performance Impact: When autogrow occurs, SQL Server needs to allocate additional disk space, which can cause a temporary performance hit. This can lead to slower response times for transactions occurring during the growth operation.

2. Unpredictable Growth Patterns: Autogrow operations can lead to fragmented storage if the database grows in small, frequent increments. This fragmentation can degrade performance over time and complicate maintenance tasks.

3. Disk Space Management: Relying on autogrow can result in unexpected disk space exhaustion, particularly if multiple databases are configured to autogrow simultaneously. This can lead to a scenario where the server runs out of disk space, affecting not only SQL Server but potentially other applications and services running on the same server.

4. Proactive Management: It is best practice to proactively manage your database size by monitoring growth patterns and manually increasing file sizes as needed during maintenance windows. This allows for better control over disk space usage and helps to maintain optimal performance.

• Initial Sizing: When creating a new database, set the initial sizes of your data and log files based on expected usage. This minimizes the need for autogrow events.
• Regular Monitoring: Regularly monitor database file sizes and growth trends. Use SQL Server performance monitoring tools to predict when additional space will be needed.
• Manual Growth: Increase file sizes manually during scheduled maintenance periods, based on the monitored growth trends, to avoid unexpected autogrow events during peak usage times.
• Optimized Autogrow Settings: Configure autogrow settings to use larger increments rather than small, frequent growths. This reduces the number of autogrow events and the associated performance impact.

By understanding and properly configuring autogrow, you can ensure it serves as an effective safety net rather than a primary growth management strategy. This approach helps maintain database performance and reliability while ensuring sufficient disk space is available to accommodate future growth.

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